Extreme Temperature Diary- Thursday December 21st, 2023/Main Topic: Remarkable Warmth at the Winter Solstice

Instead of a white Christmas, record warmth to blanket Midwest – The Washington Post

Instead of a white Christmas, record warmth to blanket Midwest

Santa Claus may want iced tea instead of hot chocolate this year

By Ian Livingston

Santa Claus may want iced tea instead of hot chocolate this Christmas while passing over the central United States. Unusually mild weather is expanding across the Lower 48 and is expected to break dozens of records as a warm Pacific weather pattern — connected to a strong El Niño event and boosted by human-caused climate change — sweeps over North America.

Many locations used to a white Christmas in the Upper Midwest and western Great Lakes will have bare ground and bask in temperatures about 30 degrees above the norm.

“We’re in uncharted weather and climate territory again in Minnesota this December,” wrote Paul Huttner, a meteorologist for Minnesota Public Radio. “This will likely be the first time on record that much of northern Minnesota has not seen a white Christmas.”

Minneapolis may set record highs on both Christmas Eve and Christmas Day as atypical warmth stretches from Texas to north of the Canadian border. Some spots could surpass calendar day record highs by 5 to 10 degrees.

Traveling for Christmas? We’ve got your city-by-city holiday forecast

Numerous record highs are set to fall daily as the warmth expands northward and eastward. Some have already been set in the Southwest United States.

Warm air to spill east into the holiday weekend

The warmth is set to spread north and east in large part because of a strong Pacific jet stream drawing mild, moisture-laden air into Canada and the northern United States. A strong, slow-moving storm system drenching southern California is also helping to pull in mild air.

On Wednesday, much of the western United States saw morning lows of 10 or more degrees above average — the beginning of a span of record-challenging warmth.

Phoenix was among southwestern cities that posted record warm morning lows. Its low of 60 degrees topped 57 degrees on the same date in 1921 and was 16 degrees above average. Both Los Angeles International Airport and its downtown weather station matched record warm lows for the date of 59 and 61 degrees, respectively.

Thursday, low temperatures at least 20 degrees above average will set records from the southern Plains into the Midwest. A smattering of additional records are a good bet Friday and Saturday in the same region as warm, moist air is pumped northward.

The most exceptional warmth is anticipated over the holiday weekend when morning lows may approach 40 degrees above normal in the Upper Midwest. Afternoon high temperatures should rise 20 to 30 degrees above normal.

Unusually mild weather will spread from Minnesota, Iowa and eastern South Dakota on Saturday toward the western half of the Great Lakes on Christmas Day. Many locations that normally post highs in the 20s and 30s at this time of year will instead be in the 40s and 50s.

Places that are forecast to see record or near record highs. (Weather Prediction Center)

Cities that could set record highs on Christmas Eve

A white Christmas is virtually out of the question in many places that are accustomed to it because of temperatures that will be way too warm. Below are some locations projected to see record highs on Christmas Eve:

  • International Falls, Minn. — Forecast is 42 or about 22 degrees above normal (record is 42 in 1994).
  • Minneapolis — Forecast is 53 or about 27 degrees above normal (record is 46 in 1957).
  • Rockford, Ill. — Forecast is 54 or about 22 degrees above normal (record is 55 in 2021).
  • Sioux Falls, S.D. — Forecast is 53 or about 24 degrees above normal (record is 50 in 2021).

Keep in mind that International Falls ordinarily has a 93 percent chance of a white Christmas and Minneapolis a 74 percent chance.

A record warm Christmas morning for many

Dozens of locations in the Upper Midwest could register their warmest Christmas mornings on record. Here are a few examples:

  • Chicago — Forecast is 48 or about 25 degrees above normal (record is 46 in 1936).
  • Duluth, Minn. — Forecast is 37 or about 30 degrees above normal (record is 34 in 1877).
  • Eau Claire, Wis. — Forecast is 44 or about 34 degrees above normal (record is 35 in 1936).

While this bout of extreme warmth is tied to the prevailing jet stream and amplified by the El Niño climate pattern, a trend toward less extreme cold in winter has a strong connection to human-caused climate change.

Historically low snow cover extent

A lack of snow is both contributing to the dearth of cold in the Lower 48 states and also an indicator of it. The Dec. 21 snow cover extent is the lowest percentage in records dating to 2003. Snow covered the ground over only 14.3 percent of the country.

There’s little indication that the snow cover will meaningfully expand in the coming days.

The snow is not only depleted in the contiguous United States but also in Canada, where it has also been historically warm.

Environment Canada announced Tuesday that numerous locations in Newfoundland and Labrador reached record highs for December as a mild East Coast storm pumped warm, moist air northward.

The snow cover over North America is also the lowest on record for the time of year and more typical of early April.

The weather pattern may shift to a more wintry one in January, although models project that Canada and the northern tier of the United States will remain somewhat milder than normal.

Jason Samenow contributed to this report.

By Ian Livingston Ian Livingston is a forecaster/photographer and information lead for the Capital Weather Gang. By day, Ian is a defense and national security researcher at a D.C. think tank. Twitter

Analysis: Winter warmth in the U.S. Midwest in the days before Christmas 2023 linked to climate change | Climate Central

Analysis: Winter warmth in the U.S. Midwest in the days before Christmas 2023 linked to climate change

For the U.S. Midwest states, chances for a White Christmas are looking slim. Climate Central analysis shows that the unusually warm wintertime temperatures forecast over the five days leading up to and including Christmas Day (December 21-25) for much of the Upper Midwest are at least twice as likely due to human-caused climate change. 

According to the National Weather Service, a White Christmas is defined as at least 1 inch of snow on the ground at 7 am local time on Christmas Day. The historic probability of a White Christmas in this part of the country runs from 40% to 90+%. See the probability for your location, with ready-to-use graphics.

What sort of unusual temperatures are forecast?

  • Daily average temperatures are expected to be 20-35°F above average (based on 1991-2020 climate normals) in some regions during this five-day period – including large parts of MinnesotaWisconsin, and Iowa
  • Daily temperatures across the Upper Midwest states are generally not expected to dip below 32°F, even at night, for most of the five days leading up to Christmas Day. With forecast temperatures above 32°F, existing snow depth is likely to melt, and conditions are not supportive of falling snow.
  • Temperatures are not expected to dip below 32°F on any day between December 21 and 25 across all of Illinois, much of Iowa, and parts of Minnesota, Wisconsin and Michigan.

What impact is climate change having?

  • During this five-day period leading up to and including Christmas Day, the unusually warm conditions have a strong climate change influence. Most days across the affected states are expected to reach a Climate Shift Index (CSI) level of at least 2, meaning that temperatures in those areas are at least two times more likely because of human-caused climate change. 
  • In large parts of MinnesotaWisconsin and Iowa, all five days in this period are expected to reach a CSI level of at least 2, while surrounding areas are expected to experience four days at or above CSI level 2.
  • Most of Michigan’s lower peninsula is expected to experience three days of at least CSI 2, while in the upper peninsula, four days are expected to reach at least a 2 on the CSI scale.
  • Some days are expected to reach a CSI level 5 in parts of Minnesota, Wisconsin, Michigan, and surrounding areas. A CSI of 5 indicates an exceptional climate event, where conditions were made at least five times more likely due to climate change.

Use the Climate Shift Index global map to see CSI levels in your city and region. 

How do we know climate change is having an impact?

The Climate Shift Index uses peer-reviewed methodology to estimate how climate change has increased the likelihood of a particular daily temperature. It can be run using historical or forecast temperatures.

Using computer models, we compared the likelihood that these temperatures would occur in a world without carbon emissions released by humans, versus in today’s world with decades of carbon emissions building up in the atmosphere. This is an established scientific method to determine how much climate change has or has not affected individual extreme weather events.

For this analysis, temperatures come from the National Center for Environmental Prediction’s Global Forecast System.

What do experts have to say?

Dr. Andrew Pershing, VP of Science at Climate Central, said: 

“People dreaming of a White Christmas will be sorely disappointed this year. As long as people keep burning coal, oil, and natural gas, events like the string of unusually warm temperatures in the Midwest will become more and more common.”

To request an interview with a Climate Central scientist, please contact Peter Girard at pgirard@climatecentral.org

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